[PATCH] drm/exynos: modify burst size based on overlay size

[Prathyush K]

The BURST size of fimd is adjusted based on the number of bytes to be
read. This is calculated based on the overlay width and the number of
bits per pixel. There are three burst lengths supported - 4 words,
8 words and 16 words where each word is 8 bytes long.

Signed-off-by: Prathyush K <prathyush.k at samsung.com>
---
 drivers/gpu/drm/exynos/exynos_drm_fimd.c |   34 ++++++++++++++++++++++--------
 1 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_fimd.c b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
index 19f12d1..655b2dd 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_fimd.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
@@ -384,6 +384,7 @@ static void fimd_win_set_pixfmt(struct device *dev, unsigned int win)
 	struct fimd_context *ctx = get_fimd_context(dev);
 	struct fimd_win_data *win_data = &ctx->win_data[win];
 	unsigned long val;
+	unsigned long bytes;
 
 	DRM_DEBUG_KMS("%s\n", __FILE__);
 
@@ -393,48 +394,63 @@ static void fimd_win_set_pixfmt(struct device *dev, unsigned int win)
 	case 1:
 		val |= WINCON0_BPPMODE_1BPP;
 		val |= WINCONx_BITSWP;
-		val |= WINCONx_BURSTLEN_4WORD;
+		bytes = win_data->fb_width >> 3;
 		break;
 	case 2:
 		val |= WINCON0_BPPMODE_2BPP;
 		val |= WINCONx_BITSWP;
-		val |= WINCONx_BURSTLEN_8WORD;
+		bytes = win_data->fb_width >> 2;
 		break;
 	case 4:
 		val |= WINCON0_BPPMODE_4BPP;
 		val |= WINCONx_BITSWP;
-		val |= WINCONx_BURSTLEN_8WORD;
+		bytes = win_data->fb_width >> 1;
 		break;
 	case 8:
 		val |= WINCON0_BPPMODE_8BPP_PALETTE;
-		val |= WINCONx_BURSTLEN_8WORD;
 		val |= WINCONx_BYTSWP;
+		bytes = win_data->fb_width;
 		break;
 	case 16:
 		val |= WINCON0_BPPMODE_16BPP_565;
 		val |= WINCONx_HAWSWP;
-		val |= WINCONx_BURSTLEN_16WORD;
+		bytes = win_data->fb_width << 1;
 		break;
 	case 24:
 		val |= WINCON0_BPPMODE_24BPP_888;
 		val |= WINCONx_WSWP;
-		val |= WINCONx_BURSTLEN_16WORD;
+		bytes = win_data->fb_width * 3;
 		break;
 	case 32:
 		val |= WINCON1_BPPMODE_28BPP_A4888
 			| WINCON1_BLD_PIX | WINCON1_ALPHA_SEL;
 		val |= WINCONx_WSWP;
-		val |= WINCONx_BURSTLEN_16WORD;
+		bytes = win_data->fb_width << 2;
 		break;
 	default:
 		DRM_DEBUG_KMS("invalid pixel size so using unpacked 24bpp.\n");
-
+		bytes = win_data->fb_width * 3;
 		val |= WINCON0_BPPMODE_24BPP_888;
 		val |= WINCONx_WSWP;
-		val |= WINCONx_BURSTLEN_16WORD;
 		break;
 	}
 
+	/*
+	 * Adjust the burst size based on the number of bytes to be read.
+	 * Each WORD of the BURST is 8 bytes long. There are 3 BURST sizes
+	 * supported by fimd.
+	 * WINCONx_BURSTLEN_4WORD = 32 bytes
+	 * WINCONx_BURSTLEN_8WORD = 64 bytes
+	 * WINCONx_BURSTLEN_16WORD = 128 bytes
+	 */
+	if (bytes < 128)
+		if (bytes < 64)
+			val |= WINCONx_BURSTLEN_4WORD;
+		else
+			val |= WINCONx_BURSTLEN_8WORD;
+	else
+		val |= WINCONx_BURSTLEN_16WORD;
+
 	DRM_DEBUG_KMS("bpp = %d\n", win_data->bpp);
 
 	writel(val, ctx->regs + WINCON(win));
-- 
1.7.0.4